1. Field of the Invention
The invention generally relates to telephony systems. In particular, the invention relates to the equalization of audio signals transmitted or received by telephony terminals within a telephony system.
2. Background
Traditional telephony systems, including analog systems such as POTS (Plain Old Telephone Service) systems and digital systems such as ISDN (Integrated Services Digital Network) systems, carry audio signals in a narrowband fashion. In such systems, the audio signal is often digitized at a data rate of 64 kilobits per second (kbps) and may be compressed to a data rate of less than 64 kbps. As a result, signal quality and fidelity is compromised. Traditional narrowband telephony thus represents a compromise between intelligibility and data rates, providing an acoustic bandwidth of approximately 200 hertz (Hz) to 3.4 kilohertz (kHz).
Wideband telephony refers to transmitting audio signals with a bandwidth in the range of approximately 50 Hz to 7 kHz, effectively doubling the narrowband audio signal of traditional telephony. Compared to narrowband telephony, the low-frequency enhancement from 50 to 200 Hz has been observed to add a sense of presence, adding increased naturalness and comfort to conversations. The high-frequency extension from 3.4 kHz to 7 kHz provides better differentiation of certain consonants and therefore provides significantly improved intelligibility. Although wideband telephony was standardized for ISDN with the G.722 codec approximately 20 years ago, it never really enjoyed wide deployment.
However, with the recent introduction of Voice over Internet Protocol (VoIP) telephony systems and other packet telephony systems that support data rates of 128 kbps or even higher, wideband telephony is now becoming more widely available. New wideband telephony systems can advantageously permit the end-to-end transmission of high-fidelity audio signals at a quality comparable to compact disc (CD) quality or even better.
Since wideband telephony systems achieve significantly-improved signal clarity, it is anticipated that some users will want to adjust the audio output to their personal liking. For example, some users may wish to fine-tune the audio output to suit a personal preference in a like manner to users who adjust the audio output of a high-fidelity stereo system. Also, for psychological reasons, some users may want to make the audio output sound more like the audio output associated with traditional narrowband telephony systems. Still further, some users may want to adjust the audio output to compensate for ambient noise or other factors that may impact their perception of the audio output.
Many conventional telephony systems provide no mechanism for shaping or equalizing an audio signal. On the other hand, some conventional telephony systems provide filters for shaping an audio signal prior to transmission over the telephony network and/or after reception but prior to playback at the speaker. Such filters may be hardware-based or software-based. However, the settings associated with such filters are preconfigured for the telephony system and are not configurable or selectable by either the person placing or receiving the telephone call. Such settings are also not configurable or selectable on a call-by-call basis. For narrowband telephony systems, this is not a significant issue, since the audio signal quality and fidelity is already compromised and control over loudness is all that is really needed. However, for wideband telephony systems, the absence of such functionality may significantly impact the user experience.
What is needed then is a system, method and apparatus that permits a user to configure or select the manner in which an audio signal transmitted or received over a wideband telephony system is shaped or equalized. The desired system, method and apparatus should allow the user to configure or select equalization control parameters on a call-by-call basis. Furthermore, the desired system, method and apparatus should allow the user to associate equalization control parameters with a party initiating a call and/or a party receiving the call, thereby facilitating automated equalizer adjustment at call connection based on an identification of the calling party and/or the called party.